This application claims the priority of 198 31 248.2, filed Jul. 11, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a sensor arrangement on a wheel suspension for a vehicle.
In vehicles, in particular in motor vehicles, such as passenger cars, trucks and buses, many vehicle-side control devices may require information concerning the relative position of a vehicle body and a pivot arm which is mounted pivotably thereon in a wheel suspension. For example, the electronic control unit of a level-control device uses the relative position between a transverse link which is coupled to a wheel and the vehicle body for each axle (or for each wheel), to determine the control input which is required in order to set a predetermined vehicle level. To ascertain this relative position, a sensor is used, which usually detects the deviation of the pivot arm from a starting position.
For example, in a sensor arrangement disclosed in German Patent Document DE 39 19 040 A1, a pivot arm is mounted pivotably on a vehicle body, and a sensor for detecting the relative position between pivot arm and vehicle body is arranged in a fixed position on the vehicle body. In order to detect the relative position between pivot arm and vehicle body, the sensor is mechanically coupled to the pivot arm.
German Patent Document DE 44 29 856 C1 discloses a sensor arrangement in which an axis of rotation of the sensor is arranged coaxially with a pivot axis of the pivot arm, about which the pivot arm of the wheel suspension is mounted pivotably on the vehicle body when the wheel suspension springs inwards and outwards.
During the assembly of a vehicle, the individual components of a wheel assembly are put together and mounted. Owing to the large number of individual parts which are put together, the manufacturing tolerances of these parts may accumulate to such an extent that it is necessary to compensate for the tolerances for the sensor in order to define a starting relative position between the pivot arm of the wheel suspension and the vehicle body. Various procedures are available for carrying out such tolerance compensation. In the case of sensors which are equipped with a longitudinally adjustable control rod, the tolerance compensation may be carried out mechanically by suitably adjusting the length of this control rod. However, to allow such tolerance compensation to be carried out, there must be sufficient space at the location where the sensor is fitted for the control rod to be adjusted manually; however, this cannot be ensured for every type of vehicle.
In the case of other sensors, the tolerance compensation may be carried out electronically, in which case the electronics in question can theoretically define any desired sensor position as the reference position. However, in the case of sensors whose structure allows only a limited measurement range in the form of deviations from a starting position to be determined, an actual installation position which in fact differs from a defined desired installation position in practice reduces the measurement range or, if the sensor electronics allow such calibration, results in a reduced measurement accuracy.
Finally, it is possible--at least in theory--for the sensor to be fitted to the finished vehicle only as virtually the last component, in order for the sensor then to be adjusted with the desired alignment while it is being installed. However, the installation conditions often do not allow this, or allow this only with a disproportionately high level of effort.
One object of the present invention is to provide a sensor arrangement of the type mentioned at the outset, with an improved tolerance compensation.
This and other objects and advantages are achieved by the sensor arrangement according to the invention, which is based on the general idea of using a common attachment point on the vehicle body for the pivot arm and the sensor. The result of this measure is that an essential relative measurement between sensor and pivot shaft is then dependent only on the manufacturing tolerances of the pivot-arm-side and sensor-side attachment elements rather than on the total tolerances of the numerous individual components which have been fitted to the wheel suspension, as with conventional sensor arrangements.
If the pivot-arm-side attachment element and the sensor-side-attachment element are then both designed to meet relatively tight tolerances, there is no need to carry out a tolerance compensation with regard to this relative arrangement between sensor and pivot arm. By way of example, a bearing of the pivot arm (pivot-arm-side attachment element) and a housing part of the sensor (sensor-side attachment element) are together attached to the vehicle body by means of a screw. The distance between the sensor and the common attachment point of the pivot arm is then independent of the actual arrangement of the attachment point on the vehicle body (which is dependent on the manufacturing and assembly tolerances of the individual parts which interact on the wheel suspension). In order to obtain the optimum alignment of the sensor relative to the pivot arm, all that then remains is to set an angle which is included between a first straight line, which runs through the attachment point and the sensor, and a second straight line, which runs through the attachment point and the point where the sensor is coupled to the pivot arm.
Thus, in the sensor arrangement according to the invention, there is no need for a tolerance compensation for the relative position of the sensor at least with regard to the distance between the sensor and the attachment point of the pivot arm. However, given a fixed distance, the required spatial arrangement of sensor in relation to pivot arm can be set relatively easily and relatively accurately. A tolerance compensation in this respect may preferably be carried out electronically, without this process significantly impairing the measurement range of the sensor or its measurement accuracy.
In a particularly advantageous embodiment of the sensor arrangement according to the invention, the sensor-side attachment element may be a sensor holder which is designed as a separate component and to which the sensor is attached. A component of this nature can be manufactured relatively inexpensively and with a high level of accuracy, for example as a stamped part, so that sensors which have been used hitherto can continue to be used without alteration. In this case, the sensor holder has first attachment means for securing the sensor to the sensor holder, and second attachment means for securing the sensor holder to the vehicle body together with the pivot-arm-side attachment element. A tolerance which is as tight as desired can then be observed for the relative position of the first and second attachment means on the sensor holder.
According to another embodiment of the sensor arrangement according to the invention, the common attachment point of sensor-side attachment element and pivot-arm-side attachment element may be formed by a bearing bolt which forms the pivot pin of the pivot arm. Moreover, in this case, the pivot-arm-side attachment element may be pivotably attached to the vehicle body by means of the bearing bolt, in which case the sensor-side attachment element has a hole, in particular a hole for the bearing bolt to fit into. This measure enables the sensor-side and pivot-arm-side attachment elements to be automatically mounted on the vehicle body, the bearing bolt attaching not only the pivot-arm-side attachment element but also the sensor-side attachment element, which has been guided or pushed onto the pivot-arm-side attachment element, to the vehicle body.
According to a further embodiment of the sensor arrangement according to the invention, it is possible to provide positioning means which are used to automatically locate a predetermined relative position of the sensor-side attachment element in relation to the vehicle body. Such positioning can be carried out mechanically in particular. Stipulation of this relative position also makes the relative position of the sensor with respect to the pivot arm dependent on the manufacturing and assembly tolerances of the individual components of the wheel suspension. However, this dependency, compared to the novel predetermined relative position between the sensor and its common attachment or articulation point with the pivot arm on the vehicle body, has considerably less influence on the adjustment of the starting relative position between pivot arm and vehicle body, so that only a slight tolerance compensation is required. This can be carried out electronically without noticeably impairing the measurement range and/or the measurement accuracy of the sensor.
It will be understood that the features mentioned above and those which are still to be explained below can be used not only in the combination given in each case but also in other combinations or as a stand-alone measure without departing from the scope of the present invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.